Iran’s most heavily fortified nuclear site is at Fordo, a hilly area south of Tehran and about 15 miles away from Qum, a city where more than a million people live.

The United States has joined Israel in its attacks on Iran’s nuclear program. The U.N.'s atomic watchdog and other experts say radiological contamination is likely inside a key uranium enrichment site at Natanz that was badly damaged by Israel and then hit by U.